Plasma reactors may include at least two electrodes which are spaced apart. Typically, a voltage difference is applied to the electrodes and an electric field is established between them. A stream of gas, or multiple streams of different gasses, and or gasses and liquids, gasses and solids or other material or combinations of materials may be introduced to the space between the electrodes such that said materials partially or completely pass through the electric field. Exposure to the electric field generally partially or completely ionizes the gas and other materials between the electrodes and creates a plasma. The systems used to create the electric field which encourages the plasma to form are herein referred to as plasma voltage generators. This novel plasma voltage generator is relevant to many plasma reactors but most relevant to dielectrically isolated plasma reactors.
The plasma voltage generators widely used in the industry are typically transformers driven by high voltages and switched to create a series of high voltage pulses. Other systems are pulse formers which are expensive and generally limited in frequency. All these systems are limited in frequency due to the recovery time of the electronics between pulses and limited in peak voltage by the input voltage and transformer characteristics. High transformer input voltages in excess of 100 volts are normally used in these systems which complicate the voltage control and the transformer drivers. These traditional plasma voltage generators generally create pulses at a frequency below 2 kHz although some may run as high as 30 kHz or higher.
New generation plasma systems need flexible plasma voltage generators which may operate at generally higher frequencies, may have the capability to modify the frequency, peak voltage, power and other operating characteristics to produce varying levels of plasma energy based on outside control factors. In addition, these plasma generators may need to react dynamically to changes in the reactor. For instance, a water remediation system may have heavy loads during peak use times and light loads during other times. In gas or gas/liquid reactors, the reactor may present a variable load to the plasma voltage driver which may need to be accounted for. The plasma voltage generator may need to be able to react to these varying conditions both independently and under the control of a microprocessor and sensor electronics.
In addition, many plasma reactors may have somewhat predictable capacitance which may be used as a circuit element for resonant and quasi-resonant plasma voltage drivers. By using the capacitive nature of the reactor, any changes in this capacitance may be used to monitor, either directly or indirectly, the reaction or condition of the reactor. In addition, since the capacitive nature of the reactor may be used as a circuit element in an inductive capacitive (LC) or other tank circuit, a resonance or partial resonance (herein referred to as quasi-resonance) may be established and used to store energy while a transformer may be used to increase this energy in the tank circuit while being switched on and off at appropriate times.
This novel plasma voltage generator treats the plasma reactor as an electrical circuit element by creating a quasi-resonant resonant oscillation using the transformer and other components in the plasma voltage generator circuit. Plasma reactors, and significantly dielectrically isolated plasma reactors exhibit a capacitive characteristic. This capacitive characteristic allows for the storage of energy in the reactor and associated components which greatly increase the energy efficiency of the plasma voltage generator. In addition, since some of the physical conditions of the reactor while in operation such as pressure, temperature, material flow through the reactor are reflected in the capacitive characteristics of the reactor, the new plasma voltage generator may be designed to sense and react to these changing characteristics in a way beneficial to the overall reaction desired. In addition this novel plasma voltage generator may allow a lower voltage input from the voltage supply, may run at generally higher frequencies, and may be dynamically controllable in peak voltage, frequency, power and other system parameters. This may be accomplished while maintaining the quasi-resonant nature of the drive.